Loud speaker mounting



March 21, 1933.

G. L.. BEERS ET AL LOUD SPEAKER MOUNTING Filed Sept. 19, 1928 INVENTOR56? ATTORNEY Patented Mar. 2l, 1933 UNITED' STATES PATENT OFFICE GEORGEL. IBEERS, 0F EAST PITTSBURGH, AND WILLIAM S. BARDEN', OF NORTH DOCK,PENNSYLVANIA, ASSIGNORS T0 WESTINGHOUSE ELECTRIC AND v:MANUFAC- TURINGCOMPANY, A CORPORATION 0F PENNSYLVANIA l LOUD SPEAKER MOUNTING iApplication led September 19, 1928. Serial No. 306,869.

Our invention relates broadly to soundreproducing apparatus and moreparticularly to apparatus of the type wherein a loud speaker issupported in the interior of a cabinet in operative relation to anopening in one of the walls thereof.

In designing combined radio sets of the console type wherein the radioreceiving apparatus and the loud speaker are contained in a single largecabinet, the problem of preventing cabinet resonance has heretofore beenextremely difficult to solve.

In certain receiving sets with which we are familiar, a loud speaker ofthe cone type is employed, the cone diaphragm being so mounted that oneof thecabinet walls constitutes a. baiie for the purpose of reinforcinglow frequencies, as `disclosed in the patent to Rice et al. No.1,631,646. In sets of-this type, however, the enclosed space at the rearof the diaphragm becomes a resonance compartment and unpleasantlyaccentuates certain low frequencies inthe output of the loud speaker.

This effect .is particularly noticeable and objectionable when the loudspeaker is reproducing masculine speech, causing the speech to assume adrum like or booming sound which is extremely unnatural.

Furthermore, since the thermionic devices used in a radio receiving setare often microphonic, as explained in the patent to Allen, No.1,401,121, the resonance phenomena in sets of the console type isaggravated by regenerative effects resulting from the transfer of soundenergy from the vloud speaker to the tubes, both through the air andthrough the walls of the cabinet.

It is, accordingly, an object of our invention to provide means wherebya loud speaker may be so mounted Within a cabinet that undesirableresonance phenomena shall be eliminated.l Y

Another object of our invention is to provide means whereby a loudspeaker may be.

so mounted within a cabinet, that also contains a radio set comprisingthermionic tubes, that sound energy from the loud speaker shall beprevented from causing effects analogous to those caused by electricalregeneration.

Another object of our invention is to provide,`in radio receivingapparatus of the console type, ymeans whereby the cabinet shall bepresented from reinforcing, through resonance, certain of the soundfrequencies existing in the output from a loud speaker supported withinthe said cabinet.

The novel features that we consider characteristic of our invention areset forth with particularity in the appended claims. The

invention itself, both as to its organization,

and its method of operation, together with additional objects and.advantages thereof will best be understood from the followingdescription of a specific embodiment, when read in connection with theaccompanying drawing.

The single figure of the drawing is a view, in perspective, of a radioreceiving set of the console type comprising a preferred embodiment ofmy invention, a door and portions of the Walls of the cabinet beingomitted to facilitate description of the device.

The apparatus illustrated inthe drawing comprises a cabinet l having atop, a bottom and a front panel 2. The rear of the cabinet issubstantially open, being merely provided with a plurality of doorswhich carry screening material 3 such as cloth or cane to prevent accessto the interior and permit exit of sound. The front panel has an opening4 extending through it which may advantageously be covered by screeningmaterial 5 of any desired type, merely f for the purpose ofornamentation.

A shelf 10 is supported within thel cabi-v whereby they may be operatedfrom the eX- terior of the cabinet.

A vertical partition 14 is disposed within the cabinet, between theshelf 10 and the bottom. thereof and is positioned from one to 'iveinches rearwardly of, and parallel to,

the frontpanel 2. The partition is provided with an opening ofsuiiicient size t0 accommodate the support therein of a large conicaldiaphragm 15 which is connected to,

' and arranged to be actuated by, electro-magshown).

of the partition 14 is in immediate contact ,with the lower surface ofthe shelf 1() while,

under other conditions, it may be desirable to leave a small openingbetween the partition and the shelf.

The front of the cabinet is provided with a plurality of doors 18 whichmay be closed when the device is not in use.

lIn the operation of the device, thel electromagnetic unit 16 causes thecone 15 to vibrate, which sets up sound waves in the air. The soundwavesescape through the screen 5 to the space outside thev cabinet. At the.

same time, sound waves upon the other side of the partition 14 arecreated by the movements of the cone 15 and pass to the space outsidethe cabinet through the screen material 3 at the back. The distance fromthe rear face of` the. partition 14 through the back of the cabinet andaround to the front face of the partition is long enough to preventinterference action between the waves set up upon the two faces of thepartition.

The region between the rear of the partition 14 and the back of/ thecabinet is b ounded at the top by the shelf and on the sides and thebottom by the walls and floor onf the cabinet. It is, therefore,somewhat like a short and wide rectangular resonance horn and has atendency to over-emphasize those frequencies to which its dimensionsrender it responsive. This tendency is largely overcome by the provisionfor leakage affordedby the passageways 17 between the edges of thepartition and the Walls of the cabinet or the Hoor or the shelf. Any airpressure created by the movement of the cone is relieved, to a certainextent, by flow of air throughr these passages. The pressure waves whichotherwise would set up resonancein the cabinet are rendered ineffectiveby the pressure relief afforded by the passages 17. Also, these passagestend to cause the partition 14 to act like a baiie which is too small,permitting some interference between the waves created on the two facesof the partition.

For best effects, the frequencies which are over-emphasized by resonanceaction of the cabinet and they frequencies for which the system isrendered somewhat inefiicient by the passages 17 should be approximatelythe same. Moreover, it is desirable that the size 0f the passages 17 andthe distance of the partition' 14 behind chosen that the elfect of thepassages and of the cabinet resonance substantially balance each other.I have found that, l for a cabinet 12 inches high and 22 inches wide and12 inches from front to back in which the shelf 10 is 7 inches above thebottom, the partition 14 is preferably 11/2 inches to the rear of thefront panel 2, the passage 17 is approximately 21/2 inches wide and theopening 4 is approximately the same size as the diaphragm 15.

With this design, there is no objectionable booming or drumming effecteven lat the lowest notes of a base voice. Moreover, the consequence oflessening the resonance in the cabinet member diminishes the mechanicalvibration imparted to the shelf 10 and thus avoids re enerative effectsthrough the mechanical viration of the vacuum tubes Many variations ofthe details herein described will occur to those skilled in the art. Alarge departure from the exact dimensions mentionedherein may be made ifthe dimensions are so chosen that the principles of our inventionareemployed. No limitation 1s intended by the specic mention of .saiddetails and dimensions. The only intended limitations are those requiredby the 'prior art or expressed in the claims.

We claim as our invention:

1. In combination, a sound-reproducing device, including a baie, acabinet that has a tendency to accentuate by resonance-chamber effect,certain of the sound frequencies that said device is capable ofreproducing, said cabinet being substantially open in the rear, saidbale being located within said cabinet and in spaced relationship withcertain of the walls of said cabinet so that said tendency to accentuateis nullied.

2. In combination, a sound-reproducing device including a ballie, acabinet having thereof, said cabinet an opening in a wall byresonance-chamber tending to accentuate,

the panel 2 should be so effect, certain of the sound frequencies thatsaid device iscapableof reproducing, said cabinet being substantiallyopen at the rear, said device being located within said cabinetrearwardly of said opening and in spaced relatidnship to certain of thewalls of said cabinet whereby said tendency to accentuate issubstantially nullified.

3. In combination, a. sound-reproducing device `comprising a relativelylare diaphragm, a baffle surrounding the diag ragm, a cabinet that tendsto accentuate, y resonance-chamber effect, at least one of the soundfrequencies that said device is capable of reproducing, said cabinetbeing substantially open at the back said device being supported withinthe cabinet by said baille, certain of the edges of said bale extendingonly into proximity to the interior surfaces of certain of the walls ofsaid cabinet, whereby said cabinet is prevented from accentuating saidfrequency during actuation of said sound-reproducingl device.

In testimony whereof, we have hereunto subscribed our names this 12thday of September, 1928.

GEORGE L. BEERS. WILLIAM S. BARDEN.

